1. Field of the Invention
The present invention relates to a new composite material comprising a substrate, at least one layer of a III-V compound and at least one layer having a metallic character. It also relates to electronic components containing this material and to a process for the production of said material.
2. Description of the Related Art
The prospects offered by components based on structures having a buried metallic layer and the physical studies on the metal/semiconductor (M/SC) multi-layer composites are the origin of the numerous studies carried out with a view to epitaxial deposition or growth of metal films on semiconductor substrates.
The work on the epitaxy of silicides on silicon, in particular by FURUKAWA, S. and by ISHIWARA, H., Jpn. J. Appl. Phys. 22, Suppl. 22-1 (1983) 21-27 and by SAITOH, S., ISHIWARA, H., ASANO, T., FURUKAWA, S., Jpn. J. Appl. Phys. 20 (1981) 1649-1656 has already led to the production of transistors based on buried metal (cf. ROSENCHER, E., DELAGE, S., CAMPIDELLI, Y., ARNAUD D'AVITAYA, F., Electron. Lett. 20 (1985) 762-764 and ARNAUD D'AVITAYA, F. DELAGE, SQ., ROSENCHER, E., DERRIEN, J., J. Vac. Sci. Technol. B 3 (1985) 770-773).
Despite the great potential value of such components and despite numerous studies, the situation is far less advanced in the case of the III-V compounds because the metal or the metal compound to be deposited or grown epitaxially must be stable to heat, in particular up to a temperature of 500.degree.-600.degree. C. to enable reepitaxy of the semiconductor.
The deposition of layers of metals such as aluminum, silver and iron has been proposed, in particular with gallium arsenide as substrate. However, on the one hand, the results are mediocre and, on the other hand, the structures formed have too low a thermal stability and too poor a mesh agreement to enable reepitaxy of the III-V compound making up the starting support on the metallic layer.
It is preferable that the interface between the metallic layer and the semiconductor layer should be abrupt, that is to say that there is a true continuous solution between the layers. However, it is permissible that the transition zone extends over at most ten monoatomic layers, advantageously at most five, and preferably at most two. The ideal is the perfect continuous or discontinuous solution.
Other tests have been carried out; for example the deposition of metals which are deliberately interacted with the substrate with the aim of obtaining, by interdiffusion in solid phase, compounds of the type M.sub.x (GaAs).sub.y, which are equivalent to silicides, on Si, or such as a co-deposition of silicon and a metal to obtain a silicide.
No success has been achieved hitherto in obtaining layers having a metallic character which are satisfactory. More recently, it has been proposed to grow epitaxial layers consisting of a compound of arsenic and ytterbium (cf. Article "Analysis of ytterbium arsenide films grown on GaAs by molecular beam epitaxy" by H. G. RICHETER, R. S. SMITH, N. HERRES, M. SEELMANN-EGGEBERT and P. WENNEKERS, Appl. Phys. Lett. 53 (2), 11 July 1988, pages 99-101). Although the results were better than those previously found, the authors have indicated that an imperfection in the epitaxial growth was evident in this case.
Moreover, the epitaxy of GaAs on a layer of rare earth(s) arsenide does not enable a homogeneous layer to be obtained.